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Lesson: Kinetic Friction

Video

14:18

Sample Question Videos

Worksheet • 25 Questions • 2 Videos

Q1:

A block is given a short push and then it slides with constant friction across a horizontal floor. Which statement best explains the direction of the force that friction applies on the moving block?

  • AFriction will be in the opposite direction to the block’s motion because molecular interactions between the block and the floor will deform the block in the opposite direction to its motion.
  • BFriction will be in the same direction as the block’s motion because molecular interactions between the block and the floor will deform the block in the direction of its motion.
  • CFriction will be in the opposite direction to the block’s motion because thermal energy generated at the interface between the block and the floor converts some of the block’s kinetic energy to potential energy.
  • DFriction will be in the same direction as the block’s motion because thermal energy generated at the interface between the block and the floor adds kinetic energy to the block.

Q2:

A 3.00 kg block slides down a ramp which is at an incline of 3 5 . 0 . The friction force between the block and the ramp is 5.20 N.

What is the coefficient of kinetic friction between the block and the ramp?

At what incline will the box slide at a constant velocity?

Q3:

A skier skies downward along a slope inclined at 1 2 . 0 below the horizontal. The coefficient of kinetic friction between her skis and the snow is 0.100.

Calculate the acceleration of the skier heading down the hill.

Find the angle of the slope down which this skier could coast at a constant velocity. Ignore air resistance.

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